1. Field of the Invention
The present invention is related to an organic electroluminescent device having organic luminous layer comprising high polymeric material and the manufacturing method. The present invention is related to an organic electroluminescent device and the manufacturing method to form organic luminous layer by a printing method.
2. Description of the Related Art
An organic luminous layer comprising organic luminescent material can be formed between two opposed electrodes. When electric current is applied to organic luminous layer, organic luminous layer emits light. Thickness of organic luminous layer is important for improvement of efficiency of luminescence. The thickness should be around 100 nm. Even more particularly, pattern of high accuracy should be formed to make a display panel.
In organic luminescent material forming organic luminous layer, there are low molecular materials and high polymeric materials. Generally, with low molecular materials, thin film can be formed by vacuum evaporation. A mask with minute pattern is used, and patterning is performed. In this approach, upsizing of the substrate results in diminishing of pattern accuracy. In addition, it is layered in vacuum, therefore, the throughput is bad.
Thus, conventionally, a high polymeric material is dissolved in solvent, and coating slip is made. Method to form thin film is tried by the wet coating method using this coating slip. Wet coating method to form thin film, include spin coating method, bar coat method, extrusion coat method, and dip coat method. It is difficult to do patterning with high accuracy by these wet coating methods. It is difficult to paint with the state that three colors were divided into of RGB by these wet coating methods. A printing method is good at formation of separated pattern. Therefore, it is thought that formation of thin film by a printing method is the more effective method.
Macromolecular organic luminescent material is dissolved in a solvent. And organic luminescence ink is made. In this case, in point of solubility of organic luminescent material, density of organic luminescent material should be around 1%. Methods to print organic luminescence ink include the following methods: Offset printing to use elastic rubber blanket (Japanese Patent Laid-Open No. 2001-93668 Official Gazette), relief printing method to use elastic rubber printing plate and resin printing plate (Japanese Patent Laid-Open No. 2001-155858 Official Gazette), ink jet method (Japanese Patent Laid-Open No. 2002-305077 Official Gazette).